[libcxx-commits] [libcxx] [libc++] Introduce _LIBCPP_COMPRESSED_ELEMENT (PR #134253)
Nikolas Klauser via libcxx-commits
libcxx-commits at lists.llvm.org
Thu Sep 18 02:32:22 PDT 2025
https://github.com/philnik777 updated https://github.com/llvm/llvm-project/pull/134253
>From 5ac6eb878088fb451db91baf649c00c188556133 Mon Sep 17 00:00:00 2001
From: Nikolas Klauser <nikolasklauser at berlin.de>
Date: Thu, 3 Apr 2025 16:10:54 +0200
Subject: [PATCH] [libc++] Introduce _LIBCPP_COMPRESSED_ELEMENT
Banane
---
libcxx/docs/ReleaseNotes/22.rst | 8 ++-
libcxx/include/__memory/compressed_pair.h | 6 ++
libcxx/include/ext/hash_map | 42 ++---------
libcxx/include/map | 49 ++-----------
libcxx/include/unordered_map | 88 +++--------------------
5 files changed, 34 insertions(+), 159 deletions(-)
diff --git a/libcxx/docs/ReleaseNotes/22.rst b/libcxx/docs/ReleaseNotes/22.rst
index e56f0a88db138..7c97d0b517d8a 100644
--- a/libcxx/docs/ReleaseNotes/22.rst
+++ b/libcxx/docs/ReleaseNotes/22.rst
@@ -59,9 +59,10 @@ Improvements and New Features
by up to 2.5x
- The performance of ``erase(iterator, iterator)`` in the unordered containers has been improved by up to 1.9x
- The performance of ``map::insert_or_assign`` has been improved by up to 2x
-
- ``ofstream::write`` has been optimized to pass through large strings to system calls directly instead of copying them
in chunks into a buffer.
+- Multiple internal types have been refactored to use ``[[no_unique_address]]``, resulting in faster compile times and
+ reduced debug information.
Deprecations and Removals
-------------------------
@@ -89,5 +90,10 @@ ABI Affecting Changes
``_LIBCPP_ABI_NO_ITERATOR_BASES``. If you are using this flag and care about ABI stability, you should set
``_LIBCPP_ABI_NO_REVERSE_ITERATOR_SECOND_MEMBER`` as well.
+- The internal types ``__map_value_compare``, ``__unordered_map_hasher``, ``__unordered_map_equal``,
+ ``__hash_map_hasher`` and ``__hash_map_equal`` have been refactored to use ``_LIBCPP_COMPRESSED_ELEMENT`` instead of
+ potentially inheriting from the types they wrap. At this point in time we are not aware of any ABI changes caused by
+ this.
+
Build System Changes
--------------------
diff --git a/libcxx/include/__memory/compressed_pair.h b/libcxx/include/__memory/compressed_pair.h
index 12163f4af61cf..d9d2720f9c9e4 100644
--- a/libcxx/include/__memory/compressed_pair.h
+++ b/libcxx/include/__memory/compressed_pair.h
@@ -80,6 +80,10 @@ class __compressed_pair_padding {
template <class _ToPad>
class __compressed_pair_padding<_ToPad, true> {};
+# define _LIBCPP_COMPRESSED_ELEMENT(T1, Initializer1) \
+ _LIBCPP_NO_UNIQUE_ADDRESS T1 Initializer1; \
+ _LIBCPP_NO_UNIQUE_ADDRESS ::std::__compressed_pair_padding<T1> _LIBCPP_CONCAT3(__padding_, __LINE__, _)
+
// TODO: Fix the ABI for GCC as well once https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121637 is fixed
# ifdef _LIBCPP_COMPILER_GCC
# define _LIBCPP_COMPRESSED_PAIR(T1, Initializer1, T2, Initializer2) \
@@ -121,6 +125,8 @@ class __compressed_pair_padding<_ToPad, true> {};
# endif
#else
+# define _LIBCPP_COMPRESSED_ELEMENT(T1, Initializer1) _LIBCPP_NO_UNIQUE_ADDRESS T1 Initializer1
+
# define _LIBCPP_COMPRESSED_PAIR(T1, Name1, T2, Name2) \
_LIBCPP_NO_UNIQUE_ADDRESS T1 Name1; \
_LIBCPP_NO_UNIQUE_ADDRESS T2 Name2
diff --git a/libcxx/include/ext/hash_map b/libcxx/include/ext/hash_map
index ae4fb7ec01c9e..70c2fbeec2959 100644
--- a/libcxx/include/ext/hash_map
+++ b/libcxx/include/ext/hash_map
@@ -206,6 +206,7 @@ template <class Key, class T, class Hash, class Pred, class Alloc>
#else
# include <__config>
# include <__hash_table>
+# include <__memory/compressed_pair.h>
# include <algorithm>
# include <ext/__hash>
# include <functional>
@@ -224,21 +225,9 @@ _LIBCPP_WARNING("Use of the header <ext/hash_map> is deprecated. Migrate to <un
namespace __gnu_cxx {
-template <class _Tp, class _Hash, bool = std::is_empty<_Hash>::value && !std::__libcpp_is_final<_Hash>::value >
-class __hash_map_hasher : private _Hash {
-public:
- _LIBCPP_HIDE_FROM_ABI __hash_map_hasher() : _Hash() {}
- _LIBCPP_HIDE_FROM_ABI __hash_map_hasher(const _Hash& __h) : _Hash(__h) {}
- _LIBCPP_HIDE_FROM_ABI const _Hash& hash_function() const { return *this; }
- _LIBCPP_HIDE_FROM_ABI size_t operator()(const _Tp& __x) const { return static_cast<const _Hash&>(*this)(__x.first); }
- _LIBCPP_HIDE_FROM_ABI size_t operator()(const typename _Tp::first_type& __x) const {
- return static_cast<const _Hash&>(*this)(__x);
- }
-};
-
template <class _Tp, class _Hash>
-class __hash_map_hasher<_Tp, _Hash, false> {
- _Hash __hash_;
+class __hash_map_hasher {
+ _LIBCPP_COMPRESSED_ELEMENT(_Hash, __hash_);
public:
_LIBCPP_HIDE_FROM_ABI __hash_map_hasher() : __hash_() {}
@@ -248,30 +237,9 @@ public:
_LIBCPP_HIDE_FROM_ABI size_t operator()(const typename _Tp::first_type& __x) const { return __hash_(__x); }
};
-template <class _Tp, class _Pred, bool = std::is_empty<_Pred>::value && !std::__libcpp_is_final<_Pred>::value >
-class __hash_map_equal : private _Pred {
-public:
- _LIBCPP_HIDE_FROM_ABI __hash_map_equal() : _Pred() {}
- _LIBCPP_HIDE_FROM_ABI __hash_map_equal(const _Pred& __p) : _Pred(__p) {}
- _LIBCPP_HIDE_FROM_ABI const _Pred& key_eq() const { return *this; }
- _LIBCPP_HIDE_FROM_ABI bool operator()(const _Tp& __x, const _Tp& __y) const {
- return static_cast<const _Pred&>(*this)(__x.first, __y.first);
- }
- _LIBCPP_HIDE_FROM_ABI bool operator()(const typename _Tp::first_type& __x, const _Tp& __y) const {
- return static_cast<const _Pred&>(*this)(__x, __y.first);
- }
- _LIBCPP_HIDE_FROM_ABI bool operator()(const _Tp& __x, const typename _Tp::first_type& __y) const {
- return static_cast<const _Pred&>(*this)(__x.first, __y);
- }
- _LIBCPP_HIDE_FROM_ABI bool
- operator()(const typename _Tp::first_type& __x, const typename _Tp::first_type& __y) const {
- return static_cast<const _Pred&>(*this)(__x, __y);
- }
-};
-
template <class _Tp, class _Pred>
-class __hash_map_equal<_Tp, _Pred, false> {
- _Pred __pred_;
+class __hash_map_equal {
+ _LIBCPP_COMPRESSED_ELEMENT(_Pred, __pred_);
public:
_LIBCPP_HIDE_FROM_ABI __hash_map_equal() : __pred_() {}
diff --git a/libcxx/include/map b/libcxx/include/map
index f428c781e5036..e5085076faf02 100644
--- a/libcxx/include/map
+++ b/libcxx/include/map
@@ -589,6 +589,7 @@ erase_if(multimap<Key, T, Compare, Allocator>& c, Predicate pred); // C++20
# include <__memory/addressof.h>
# include <__memory/allocator.h>
# include <__memory/allocator_traits.h>
+# include <__memory/compressed_pair.h>
# include <__memory/pointer_traits.h>
# include <__memory/unique_ptr.h>
# include <__memory_resource/polymorphic_allocator.h>
@@ -633,47 +634,9 @@ _LIBCPP_PUSH_MACROS
_LIBCPP_BEGIN_NAMESPACE_STD
-template <class _Key,
- class _CP,
- class _Compare,
- bool = is_empty<_Compare>::value && !__libcpp_is_final<_Compare>::value>
-class __map_value_compare : private _Compare {
-public:
- _LIBCPP_HIDE_FROM_ABI __map_value_compare() _NOEXCEPT_(is_nothrow_default_constructible<_Compare>::value)
- : _Compare() {}
- _LIBCPP_HIDE_FROM_ABI __map_value_compare(_Compare __c) _NOEXCEPT_(is_nothrow_copy_constructible<_Compare>::value)
- : _Compare(__c) {}
- _LIBCPP_HIDE_FROM_ABI const _Compare& key_comp() const _NOEXCEPT { return *this; }
- _LIBCPP_HIDE_FROM_ABI bool operator()(const _CP& __x, const _CP& __y) const {
- return static_cast<const _Compare&>(*this)(__x.first, __y.first);
- }
- _LIBCPP_HIDE_FROM_ABI bool operator()(const _CP& __x, const _Key& __y) const {
- return static_cast<const _Compare&>(*this)(__x.first, __y);
- }
- _LIBCPP_HIDE_FROM_ABI bool operator()(const _Key& __x, const _CP& __y) const {
- return static_cast<const _Compare&>(*this)(__x, __y.first);
- }
- _LIBCPP_HIDE_FROM_ABI void swap(__map_value_compare& __y) _NOEXCEPT_(__is_nothrow_swappable_v<_Compare>) {
- using std::swap;
- swap(static_cast<_Compare&>(*this), static_cast<_Compare&>(__y));
- }
-
-# if _LIBCPP_STD_VER >= 14
- template <typename _K2>
- _LIBCPP_HIDE_FROM_ABI bool operator()(const _K2& __x, const _CP& __y) const {
- return static_cast<const _Compare&>(*this)(__x, __y.first);
- }
-
- template <typename _K2>
- _LIBCPP_HIDE_FROM_ABI bool operator()(const _CP& __x, const _K2& __y) const {
- return static_cast<const _Compare&>(*this)(__x.first, __y);
- }
-# endif
-};
-
template <class _Key, class _CP, class _Compare>
-class __map_value_compare<_Key, _CP, _Compare, false> {
- _Compare __comp_;
+class __map_value_compare {
+ _LIBCPP_COMPRESSED_ELEMENT(_Compare, __comp_);
public:
_LIBCPP_HIDE_FROM_ABI __map_value_compare() _NOEXCEPT_(is_nothrow_default_constructible<_Compare>::value)
@@ -685,7 +648,7 @@ public:
_LIBCPP_HIDE_FROM_ABI bool operator()(const _CP& __x, const _CP& __y) const { return __comp_(__x.first, __y.first); }
_LIBCPP_HIDE_FROM_ABI bool operator()(const _CP& __x, const _Key& __y) const { return __comp_(__x.first, __y); }
_LIBCPP_HIDE_FROM_ABI bool operator()(const _Key& __x, const _CP& __y) const { return __comp_(__x, __y.first); }
- void swap(__map_value_compare& __y) _NOEXCEPT_(__is_nothrow_swappable_v<_Compare>) {
+ _LIBCPP_HIDE_FROM_ABI void swap(__map_value_compare& __y) _NOEXCEPT_(__is_nothrow_swappable_v<_Compare>) {
using std::swap;
swap(__comp_, __y.__comp_);
}
@@ -747,9 +710,9 @@ struct __lazy_synth_three_way_comparator<__map_value_compare<_Key, _MapValueT, _
};
# endif // _LIBCPP_STD_VER >= 14
-template <class _Key, class _CP, class _Compare, bool __b>
+template <class _Key, class _CP, class _Compare>
inline _LIBCPP_HIDE_FROM_ABI void
-swap(__map_value_compare<_Key, _CP, _Compare, __b>& __x, __map_value_compare<_Key, _CP, _Compare, __b>& __y)
+swap(__map_value_compare<_Key, _CP, _Compare>& __x, __map_value_compare<_Key, _CP, _Compare>& __y)
_NOEXCEPT_(_NOEXCEPT_(__x.swap(__y))) {
__x.swap(__y);
}
diff --git a/libcxx/include/unordered_map b/libcxx/include/unordered_map
index a38e5e0f1b94f..3c19d6f2a7f0d 100644
--- a/libcxx/include/unordered_map
+++ b/libcxx/include/unordered_map
@@ -600,6 +600,7 @@ template <class Key, class T, class Hash, class Pred, class Alloc>
# include <__memory/addressof.h>
# include <__memory/allocator.h>
# include <__memory/allocator_traits.h>
+# include <__memory/compressed_pair.h>
# include <__memory/pointer_traits.h>
# include <__memory/unique_ptr.h>
# include <__memory_resource/polymorphic_allocator.h>
@@ -643,34 +644,9 @@ _LIBCPP_PUSH_MACROS
_LIBCPP_BEGIN_NAMESPACE_STD
-template <class _Key,
- class _Cp,
- class _Hash,
- class _Pred,
- bool = is_empty<_Hash>::value && !__libcpp_is_final<_Hash>::value>
-class __unordered_map_hasher : private _Hash {
-public:
- _LIBCPP_HIDE_FROM_ABI __unordered_map_hasher() _NOEXCEPT_(is_nothrow_default_constructible<_Hash>::value) : _Hash() {}
- _LIBCPP_HIDE_FROM_ABI __unordered_map_hasher(const _Hash& __h) _NOEXCEPT_(is_nothrow_copy_constructible<_Hash>::value)
- : _Hash(__h) {}
- _LIBCPP_HIDE_FROM_ABI const _Hash& hash_function() const _NOEXCEPT { return *this; }
- _LIBCPP_HIDE_FROM_ABI size_t operator()(const _Cp& __x) const { return static_cast<const _Hash&>(*this)(__x.first); }
- _LIBCPP_HIDE_FROM_ABI size_t operator()(const _Key& __x) const { return static_cast<const _Hash&>(*this)(__x); }
-# if _LIBCPP_STD_VER >= 20
- template <typename _K2>
- _LIBCPP_HIDE_FROM_ABI size_t operator()(const _K2& __x) const {
- return static_cast<const _Hash&>(*this)(__x);
- }
-# endif
- _LIBCPP_HIDE_FROM_ABI void swap(__unordered_map_hasher& __y) _NOEXCEPT_(__is_nothrow_swappable_v<_Hash>) {
- using std::swap;
- swap(static_cast<_Hash&>(*this), static_cast<_Hash&>(__y));
- }
-};
-
template <class _Key, class _Cp, class _Hash, class _Pred>
-class __unordered_map_hasher<_Key, _Cp, _Hash, _Pred, false> {
- _Hash __hash_;
+class __unordered_map_hasher {
+ _LIBCPP_COMPRESSED_ELEMENT(_Hash, __hash_);
public:
_LIBCPP_HIDE_FROM_ABI __unordered_map_hasher() _NOEXCEPT_(is_nothrow_default_constructible<_Hash>::value)
@@ -692,60 +668,16 @@ public:
}
};
-template <class _Key, class _Cp, class _Hash, class _Pred, bool __b>
+template <class _Key, class _Cp, class _Hash, class _Pred>
inline _LIBCPP_HIDE_FROM_ABI void
-swap(__unordered_map_hasher<_Key, _Cp, _Hash, _Pred, __b>& __x,
- __unordered_map_hasher<_Key, _Cp, _Hash, _Pred, __b>& __y) _NOEXCEPT_(_NOEXCEPT_(__x.swap(__y))) {
+swap(__unordered_map_hasher<_Key, _Cp, _Hash, _Pred>& __x, __unordered_map_hasher<_Key, _Cp, _Hash, _Pred>& __y)
+ _NOEXCEPT_(_NOEXCEPT_(__x.swap(__y))) {
__x.swap(__y);
}
-template <class _Key,
- class _Cp,
- class _Pred,
- class _Hash,
- bool = is_empty<_Pred>::value && !__libcpp_is_final<_Pred>::value>
-class __unordered_map_equal : private _Pred {
-public:
- _LIBCPP_HIDE_FROM_ABI __unordered_map_equal() _NOEXCEPT_(is_nothrow_default_constructible<_Pred>::value) : _Pred() {}
- _LIBCPP_HIDE_FROM_ABI __unordered_map_equal(const _Pred& __p) _NOEXCEPT_(is_nothrow_copy_constructible<_Pred>::value)
- : _Pred(__p) {}
- _LIBCPP_HIDE_FROM_ABI const _Pred& key_eq() const _NOEXCEPT { return *this; }
- _LIBCPP_HIDE_FROM_ABI bool operator()(const _Cp& __x, const _Cp& __y) const {
- return static_cast<const _Pred&>(*this)(__x.first, __y.first);
- }
- _LIBCPP_HIDE_FROM_ABI bool operator()(const _Cp& __x, const _Key& __y) const {
- return static_cast<const _Pred&>(*this)(__x.first, __y);
- }
- _LIBCPP_HIDE_FROM_ABI bool operator()(const _Key& __x, const _Cp& __y) const {
- return static_cast<const _Pred&>(*this)(__x, __y.__get_value().first);
- }
-# if _LIBCPP_STD_VER >= 20
- template <typename _K2>
- _LIBCPP_HIDE_FROM_ABI bool operator()(const _Cp& __x, const _K2& __y) const {
- return static_cast<const _Pred&>(*this)(__x.first, __y);
- }
- template <typename _K2>
- _LIBCPP_HIDE_FROM_ABI bool operator()(const _K2& __x, const _Cp& __y) const {
- return static_cast<const _Pred&>(*this)(__x, __y.__get_value().first);
- }
- template <typename _K2>
- _LIBCPP_HIDE_FROM_ABI bool operator()(const _Key& __x, const _K2& __y) const {
- return static_cast<const _Pred&>(*this)(__x, __y);
- }
- template <typename _K2>
- _LIBCPP_HIDE_FROM_ABI bool operator()(const _K2& __x, const _Key& __y) const {
- return static_cast<const _Pred&>(*this)(__x, __y);
- }
-# endif
- _LIBCPP_HIDE_FROM_ABI void swap(__unordered_map_equal& __y) _NOEXCEPT_(__is_nothrow_swappable_v<_Pred>) {
- using std::swap;
- swap(static_cast<_Pred&>(*this), static_cast<_Pred&>(__y));
- }
-};
-
template <class _Key, class _Cp, class _Pred, class _Hash>
-class __unordered_map_equal<_Key, _Cp, _Pred, _Hash, false> {
- _Pred __pred_;
+class __unordered_map_equal {
+ _LIBCPP_COMPRESSED_ELEMENT(_Pred, __pred_);
public:
_LIBCPP_HIDE_FROM_ABI __unordered_map_equal() _NOEXCEPT_(is_nothrow_default_constructible<_Pred>::value)
@@ -780,9 +712,9 @@ public:
}
};
-template <class _Key, class _Cp, class _Pred, class _Hash, bool __b>
+template <class _Key, class _Cp, class _Pred, class _Hash>
inline _LIBCPP_HIDE_FROM_ABI void
-swap(__unordered_map_equal<_Key, _Cp, _Pred, _Hash, __b>& __x, __unordered_map_equal<_Key, _Cp, _Pred, _Hash, __b>& __y)
+swap(__unordered_map_equal<_Key, _Cp, _Pred, _Hash>& __x, __unordered_map_equal<_Key, _Cp, _Pred, _Hash>& __y)
_NOEXCEPT_(_NOEXCEPT_(__x.swap(__y))) {
__x.swap(__y);
}
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